Spokesman Col. Tamer el-Rifaai said that forces also arrested five militants and 680 others including "criminal elements" and people suspected of supporting militants. He spoke at a press conference in the presence of senior military and Interior Ministry officials.

El-Rifaai also said that forces found and destroyed hundreds of militant hideouts, targets and explosive devices.

The casualty figures couldn't be independently verified as journalists and independent investigators are banned from accessing the turbulent Sinai region.

The massive security campaign that began on Friday covers north and central Sinai and parts of Egypt's Nile Delta and the Western Desert, along the porous border with Libya which authorities contend that Islamic militants and smugglers use as their route into the country. The operation involves land, sea and air forces. Authorities are not saying how long the operation will last.

Earlier on Thursday, the army said that airstrikes in the Western Desert destroyed 10 SUVs laden with weapons and ammunition.

Egypt has for years been struggling to contain the insurgency concentrated in north Sinai, spearheaded by a local affiliate of the Islamic State group. Militant attacks have generally surged since the 2013 military ouster of elected Islamist President Mohammed Morsi following mass protests against his divisive one-year rule. The violence has also spread to the mainland.